Technologists and computer science experts are warning that artificial intelligence poses threats to humanity’s survival on par with nuclear warfare and global pandemics, and even business leaders who are fronting the charge for A.I. are cautioning about the technology’s existential risks.

Sam Altman, CEO of ChatGPT creator OpenAI, is one of over 300 signatories behind a public “statement of A.I. risk” published Tuesday by the Center for A.I. Safety, a nonprofit research organization. The letter is a short single statement to capture the risks associated with A.I.:

“Mitigating the risk of extinction from A.I. should be a global priority alongside other societal-scale risks such as pandemics and nuclear war.”

The letter’s preamble said the statement is intended to “open up discussion” on how to prepare for the technology’s potentially world-ending capabilities. Other signatories include former Google engineer Geoffrey Hinton and University of Montreal computer scientist Yoshua Bengio, who are known as two of the Godfathers of A.I. due to their contributions to modern computer science. Both Bengio and Hinton have issued several warnings in recent weeks about what dangerous capabilities the technology is likely to develop in the near future. Hinton recently left Google so that he could more openly discuss A.I.’s risks.

It isn’t the first letter calling for more attention to be paid to the possible disastrous outcomes of advanced A.I. research without stricter government oversight. Elon Musk was one of over 1,000 technologists and experts to call for a six-month pause on advanced A.I. research in March, citing the technology’s destructive potential.

And Altman warned Congress this month that sufficient regulation is already lacking as the technology develops at a breakneck pace.

The more recent note signed by Altman did not outline any specific goals like the earlier letter, other than fostering discussion. Hinton said in an interview with CNN earlier this month that he did not sign the March letter, saying that a pause on A.I. research would be unrealistic given the technology has become a competitive sphere between the U.S. and China.

“I don’t think we can stop the progress,” he said. “I didn’t sign the petition saying we should stop working on A.I because if people in America stop, people in China wouldn’t.”

But while executives from leading A.I. developers including OpenAI and even Google have called on governments to move faster on regulating A.I., some experts warn that it is counter-productive to discuss the technology’s future existential risks when its current problems, including misinformation and potential biases, are already wreaking havoc. Others have even argued that by publicly discussing A.I.’s existential risks, CEOs like Altman have been trying to distract from the technology’s current issues which are already creating problems, including facilitating the spread of fake news just in time for a pivotal election year.

But A.I.’s doomsayers have also warned that the technology is developing fast enough that existential risks could become a problem faster than humans can keep tabs on. Fears are growing in the community that superintelligent A.I., which would be able to think and reason for itself, is closer than many believe, and some experts warn that the technology is not currently aligned with human interests and well-being.

Hinton said in an interview with the Washington Post this month that the horizon for superintelligent A.I. is moving up fast and could now be only 20 years away, and now is the time to have conversations about advanced A.I.’s risks.

“This is not science fiction,” he said.